The Obama administration will try to revive its push for tighter restrictions on firearms, almost two months after legislation seen as the best hope for gun control went down to defeat in the Senate.

The effort got an extra boost on Wednesday as families of children and educators killed at Newtown returned to Capitol Hill ahead of the six-month anniversary of the shootings to plead with lawmakers not to forget their loved ones.

"It's been the longest six months of my entire life, but also the shortest. Time becomes completely irrelevant in some respects," said Nicole Hockley, who lost her son, six-year-old Dylan, in the Dec. 14 shooting.

"Six months, six minutes, six years -- a marathon already," said Bill Sherlach, who lost his wife. "We really have no choice, because I'll spend the rest of my life without my wife."

They spoke during a meeting with Sen. Joe Manchin, D-W.Va., who spearheaded the background check compromise that failed to pass the Senate in April.

They insist that momentum for new gun control laws hasn't faded. But Congress is largely consumed by an emerging immigration reform debate -- and Manchin couldn't say whether there would be another gun vote this year, or even before the end of this congressional session at the end of 2014.

Still, Vice President Joe Biden has vowed to keep pushing for new legislation, inviting gun violence groups to a meeting at the White House on June 17.

The administration’s renewed effort will be fought on several fronts: at the White House, on Capitol Hill, and in key states and congressional districts throughout the country.

The families also met today with House GOP leaders, whose discretion will be key in determining whether any gun proposal even comes up for a vote in the House, should a bill make it out of the Senate.

“The families have asked to meet with us,” House Speaker John Boehner, R-Ohio, said on Wednesday ahead of the meeting. “Our hearts and souls go out to these families and the tragedy they've all been through.”

It's the first time Boehner will meet with the Newtown families.

On Thursday, the families will hold a press conference outside of the Capitol with senior lawmakers to mark the six-month anniversary of the shootings.

It’s unclear, though, whether the intervening two months since the last vote in Congress on gun control has changed the politics of the issue very much. In that vote, the Senate fell six votes short of the 60 they needed to advance a more modest, bipartisan gun control proposal that would have expanded background checks to firearms sales online and at gun shows. Gone from the package were proposed bans on assault weapons, and high-capacity magazines.

The proposal that the Senate scuttled remains broadly popular; a New York Times/CBS News poll earlier this month found that 69 percent of Americans – including 58 percent of Republicans – said that Congress should pass the expanded background check proposal if it comes up for another vote.

Politico Playbook: NYC Mayor Michael Bloomberg is digging in his heels on gun control and asking Democratic donors in New York to not support four Democratic senators who voted against reform. Politico's Mike Allen discusses.

In the two months since the vote, proponents of gun control have sought to ratchet up the pressure on key lawmakers. Mayors Against Illegal Guns, the pro-gun control group founded by New York City Mayor Michael Bloomberg, ran ads targeting key senators like Mark Pryor, D-Ark., and Kelly Ayotte, R-N.H., for voting against the bipartisan proposal (“Manchin-Toomey”) in April.

The results have been mixed.

In Pryor’s case, he sought to turn the attack back toward his advantage, launching his own re-election campaign ad declaring his independence from “the mayor of New York City.” Ayotte became more of a lightning rod, as gun control advocates swarmed her town hall meetings during a recess, while the National Rifle Association ran ads in her state lionizing the first-term senator.

Bloomberg’s group makes up the third front on which the renewed push for gun control will be fought.

Mayors Against Illegal Guns announced Wednesday that it planned a summer bus tour that would make at least 25 stops in key states and districts across the country, with the goal of galvanizing support for new gun control proposals.

“When senators vote down a bill with such overwhelming support among the public, there is going to be a sense of outrage. And we've seen that outrage since April 17,” said John Feinblatt, an adviser to Bloomberg. “I think Americans feel as though Congress did not represent them on April 17.”

Bloomberg is also looking to target lawmakers where it maybe hurts the most: their bank accounts.

The mayor wrote Democratic donors in New York – one of the largest wellsprings of campaign donations – urging them to refuse supporting Democratic senators who had voted against the Manchin-Toomey proposal.

“It is usual practice for elected officials all over this country to make New York once of their first stops in scooping up donations for their campaigns,” Feinblatt said. “Mayor Bloomberg thought it was important that Donors in New York be made aware of votes that senators took on April 17 to deny the Manchin-Toomey bill.”

Manchin said that Bloomberg's efforts weren't as effective as they could be, though he declined to criticize the mayor's efforts.

"I need help in going into gun regions such as West Virginia and all over this country to tell the law abiding gun owners actually what this will do for them," Manchin said. "There's going to be an election in 2014 - that's the time."